Chucking mechanism



April 6, 1943..l R. l-. cRAMER CHUCKING MECHANISM y Original Filed July 50,` i940 2 Sheets-Sheet 2 Flc?` 3 /9//5/4 TTU/@NEX Patented Apr. 6, 1943 CHUCKING MECEANISM l Raymond H. Cramer, Newark, N. J., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Original application July 30, 1940, Serial No. 348,398. Divided and this application March 13, 1941, Serial N0. 383,199

13 Claims. (Cl. 279-107) This invention relates to chucking mechanism and comprises all of the features and aspects of novelty herein disclosed. An object of the invention is to provide an improved chuck more especially for clamping a hollow work-piece for a machining operation on an exterior face. Another object is to provide improved centering mechanism for centering the work prior to clamping. Another object is to provide a chuck in which the parts are extremely compact and operate to center and rmly grip the Work in a reliable manner.

To these ends and also to improve generally upon devices of this character, the invention consists in the various matters hereinafter described and claimed. In its broader aspects, the invention is not necessarily limited to the specic construction selected for illustrative purposes in the accompanying drawings in which Fig. 1 is chiefly a horizontal axial section of a The work head comprises a housing l in which a hollow spindle I2' is journalled for rotation by bearing sleeves I4 and I6 having bearing inserts I8. Endwise movement of the spindle is prevented by a pair of preloaded ball bearings 20 arranged back to back, the inner race rings being clamped on the spindle by a nut and the outer race rings being clamped between a ange on a bearing housing 22 and a dished cap 24. 'I'he spindle is driven by a belt Ypulley 26 enclosed within a guard28. At the chuck end, the spindle has a flange 3i) carrying a water slinger 32 lapping over a drain groove on the housing.

Fastened to the flange 39 by bolts 34 is a chuck body-3B having an abutment face .38 Ato abut against one end of the work piece W, and beyond the face 38 is a circular seat, or nose portion 40 to loosely enter the work. The nose portion has aplurality of openings (preferably three) to loosely receive centering balls 42 which engage 'i'nclines 44 in longitudinal grooves on-the exterior of a Vcentering sleeve 46 which is slidable within the chuck. The sleeve is urged to centering position by coil springs 48 engaging a thrust -plate 50 fastened by screws to the, inner end of the sleeve. I'he1sleeveisadapted to be moved out of .centering positionby afcollar. oradjusting nut 52 on a draw rod 54 when the latter is moved outwardly to Work releasing position.

A round bar which is diametrically slotted is removably attached to the end of the draw rod by a threaded stud 56, the slot extending lengthwise nearly for the full length of the bar and so leaving unbroken end walls 58 and 6|). Fitting side by side in the slot is a pair of flat sided Shanks 62 carrying outwardly projecting clamping fingers 64, the latter having their ends extended laterally as indicated in Fig. 2 and so adapted to cla-mp against an ample area at the outer end of the work W. The work W is herein shown as the inner race ring of a tapered roller bearing. The Shanks (i2-have rounded inner ends engaging the interior of the centering sleeve 46 to freely rock therein into clamping position when little lugs 66 on the Shanks run along an inclined cam surface 68 at the end of the sleeve, as when the draw rod is pulled inwardly. Another lug 'lll on each shank enters a recess in the sleeve and is adapted to engage an inclined cam surface 'l2 to release the clamping fingers when the draw rod is moved outwardly. The end walls 58 and 6D compel the clamping members to move with the slotted bar when the latter is moved endwise by the draw rod but there is some lost motion. To swing freely, the Shanks are rounded at their outer ends where they engage the wall 6e. There is a lost motion space between the nut 52' and the thrust plate 53 so that the ngers release the work before the centering balls 42 release it. When chucking, the nut 52 releases the thrust plate 5B and sleeve 46 at once so that the balls center the work before the iingers grip it. Y

The draw rod 54 rotates with the hollow spindle l2 and its chuck and is always urged towards clamping position by a spring 'I8 interposed between an adjusting nut 8U on the draw rod and a shoulder at the bottom of a counterbore in the spindle. The draw rod can be forced outwardly to the right by a lever 82 pivoted at 84 to a fulcrum block 86 fastened to a supporting bar 88 on the work head. The free end of the lever has an oversize hole for a pivot pin 90 by which it is pivotally connected to a turnbuckle 52, the turnbuckle beingvconnected to a piston rod 90 projecting from an operating cylinder 96. The piston rod swings the lever 82 to cause a iounded surface on the lever to engage the nut action, a block |02 is clamped to the piston rod and carries a pivoted dog |04 which is urged towards a stop pin |0t` by a light coil spring. When the piston rod moves to the right, the dog will swing away from the stop pin and ride idly along a pivoted lever |88. The lever is urged towards a stop pin H0 by the switch plunger 98. When the piston rod moves to the left, the dog cannot swing beyond its stop pin |06 so that it positively engages a cam incline I |2 on the lever |08 and operates the switch. The switch operates devices not shown, such as a solenoid which reverses a valve controlling the action of a work loading cylinder so that chucking will be timed with the loading operation.

Figure 3 indicates a modication whereby greater spring pressure can be applied to the draw rod to supplement the spring 18. The draw rod 54 is extended through a double tapered hole |14 in the lever 82 and is threaded to receive an adjusting nut IIS. A coil spring H8 is interposed between the nut and a anged sleeve |20 through which the draw rod can slide. The sleeve |20 carries a ball thrust bearing |22 one race ring of which bears against the flange of the sleeve and the other race ring bearing against a rounded surface on the lever 82, the sleeve clearing the lever by reason of its tapering hole H4. The thrust bearing has a casing |24 supporting a shield |26 which encloses the spring and associated elements. As described in the parent case, this auxiliary spring pressure may be omitted as shown in Fig. 1.

I claim: f

l. In a device of the character indicated, a y

chuck, a hollow spindle for rotating the chuck, a draw bar slidable within the spindle, a diametrically slotted bar connected to the draw bar and having end walls, angular clamping ngers hav- Ving shanks tting side by side within and exu ltending lengthwise of the slot from one end wall substantially to the other for axial shifting thereby, and a cam face for swinging the ngers against a work-piece upon shifting movement of the draw bar with the Shanks.

2. In a device of the character indicated, a chuck, a hollow spindle for rotating the chuck, a draw bar slidable within the spindle, a slotted bar within the chuck and connected to the draw bar, clamping fingers having Shanks fitting side by side in the slot and extending from one end cf the slot substantially to the other, a cam face surrounding the Shanks, and means for actuatmg the draw bar to move the Shanks along the surrounding cam face and thereby cause the fingers to clamp a work-piece.

3. In a device of the character indicated, a chuck, a slotted bar within the chuck and movable axially thereof, clamping ngers having Shanks received in the slot, the shanks having rounded ends and being rockable in the slot upon said rounded ends, lugs on the shanks, a cam face surrounding the Shanks and lying in the path of the lugs, the slotted bar having an outer end wall retaining the Shanks, and means kior shifting the slotted bar to force the end wall against the outer ends of the shanks to shift the shan-ks axially and thereby cause the lugs to engage the cam face.

4. In a device of the character indicated, a chuck, a slotted bar within the chuck and movable axially thereof, the slotted bar having an outer end wall, -rockable clamping fingers having shanks extending lengthwise of lthe slot and up vto said outer end wall, a sleeve ysurrounding Cil the Shanks and the slotted bar, the sleeve having a cam face, the ngers projecting outwardly from the shanks, and means for shifting the slotted bar to force the end wall against the outer ends of the shanks to shift the latter axially within the sleeve and thereby cause the cam face to react on other portions of the Shanks and actuate the clamping ngers.

5. In a device of the character indicated, a chuck having a hollow nose provided with openings, centering balls within the openings, a sleeve shiftable within the nose and having cam faces engaging the balls, angular work clamping members having actuating mechanism passing through the sleeve, a thrust plate secured to the sleeve, a spring .engaging the thrust plate to shift the sleeve within the nose, and means for controlling the actuation of the thrust plate and the angular clamping members in succession.

6. In a device of the character indicated, a chuck having a hollow nose provided with openings, centering balls within the openings, a sleeve shiftable within the nose and having cam faces engaging the balls, a thrust plate secured to the sleeve, a .spring engaging one side of the thrust plate, and a member shiftable axially of the chuck to engage the other side of the thrust plate.

7. In a device of the character indicated, a chuck having a hollow nose provided with openings, centering balls within the openings, a sleeve shiftable within the nose and having cam faces engaging the balls, a slotted bar slidable within the sleeve, clamping ngers having shanks rockably mounted in the slot, and means for successively expanding the centering balls and swinging the clamping iingers against a `workpiece.

8. In a machine of the character indicated, a chuck having a hollow nose to receive a workpiece, radially movable centering means having an actuating sleeve slidable axially within the nose, a slotted bar slidable axially within the sleeve, Shanks tting side by side within the slot and having rounded ends to rock within the sleeve, clamping fingers projecting from the shanks across the end of the nose, and means for axially sliding the sleeve and the slotted bar to center the work-piece and clamp it.

9. Ina machine of the character indicated, a chuck having a hollow nose to project into a hollow work-piece, an abutment for one end of the works-piece, means comprising members movable radially through the nose for centering the work-piece thereon, clamping members having Shanks within the nose and having projecting clamping ngers to engage the opposite end of the Work-piece, and means for causing the centering members to move radially and center the work-piece prior to the action of the clamping members.

l0. In a machine of the character indicated, a chuck having a hollow nose to project loosely into a hollow work-piece, radially movable centering means having an actuating sleeve slidable within the nose for centering the work-piece thereon, clamping members extending through the sleeve and having fingers projecting beyond the end of the nose, and means for successively actuating the centering means and the clamping members.

11. Ina machine of the characterindicated, a chuck having an abutment for one end of a workpiece, the chuck. havinga portion projecting beyondzthe .abutment and provided with openings,

i extended areas thereof, a cam outside of the Shanks, and means for shifting the shanks endwise into co-operative engagement with the cam for rocking the clamping members to cause said fingers to engage the other end of the Work-piece. 13. In a device of the character described, a chuck, a diametrically slotted bar shiftable axially of the chuck and having end walls dening the ends of the slot, angular clamping members having shanks rockable Within the slot and extending from one end wall substantially to the other to provide for axial shifting movement of the Shanks in opposite directions with the bar, and cam faces surrounding the Shanks and acting upon said axial shifting movement to rock said clamping members with respect to the Work-piece.

RAYMOND H. CRAMER. 

